INCREMENTAL BIAS IN FINAPRES ESTIMATION OF BASE-LINE BLOOD-PRESSURE LEVELS OVER TIME

Finapres finger blood pressure monitoring appears to provide a reliabl e alternative to intra-arterial blood pressure measurement under many circumstances. However, few studies have focused on the limitations of Finapres assessment. In a previous pilot investigation, we observed t hat Finapres pressure following mental stressors failed to return to i nitial resting levels. Our objectives in the present study were to (1) replicate earlier findings, (2) examine whether local changes in the measured finger were responsible for the observed drift, and (3) test a method to facilitate the return of pressure to systemic baseline lev els. We studied two groups of healthy subjects who underwent a protoco l consisting of two mental stressors pre ceded and followed by baselin e periods. In the control group, the Finapres continuously monitored p ressure on a single finger for the entire protocol. The intervention g roup periodically had the Finapres cuff removed and the measured finge r exercised to prevent local changes that might influence Finapres est imation of blood pressure. Comparisons indicated a group x baseline in teraction effect for systolic and diastolic pressures (P < .0004 and P < .003, respectively). The group with the exercise intervention showe d much greater recovery during the final baseline than the control gro up. Recovery of pressures in the control group but not the interventio n group was inversely related to the stress level of blood pressure (r = .86, P < .0002), indicating a relationship between blood pressure r ise and the degree of distortion of subsequent baseline values. On the basis of our results, we propose that in prolonged protocols, the mea surement finger be exercised to facilitate accurate measurements of fi nger pressure with the Finapres.